Advanced communication earpiece device and method

ABSTRACT

An earpiece device ( 10, 110, 210, 210′ ) provides advanced communication to the user thereof, for controlling a total sound dose (TND), including an audio output from an audio source ( 16 ) reaching an ear of the user occluded at the outer ear canal ( 15 ) by an in-ear device ( 14 ), for allowing an external ambient sound to be heard by the ear of the user, and for allowing a voice (NSV) of the user to be transmitted to a telecommunication transmission link (TTL). The present invention also contemplates a method of operation of the earpiece device ( 10, 110, 210, 210′ ).

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of pending patentapplication Ser. No. 13/991,258 filed on Sep. 16, 2013, which is anational phase entry of PCT application No. PCT/CA2011/001312 filed onDec. 1, 2011, which claims priority benefit of provisional applicationfor patent No. 61/344,977 filed on Dec. 1, 2010, all of which beingincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to earpiece devices and is moreparticularly concerned with an earpiece device providing advancedcommunication to the user thereof, and method of operation thereof.

BACKGROUND OF THE INVENTION

The noisy environment in our industrial society is a health hazard tonumerous workers as well as to people engaged in recreational activitiesgenerating loud noises, or simply listening to music with varying volumesettings from individual digital music players such as an Ipod™, MP3players or the like, via a set of earphones or the like.

Many documents such as U.S. Pat. No. 3,789,952 granted to Widegren etal., U.S. Pat. No. 7,151,835 granted to Yonovitz et al., US patentpublication No. 2009/0208024 A1 to Farver and European patent No. EP1,816,892 B2 to Ruwisch aim at limiting the harm produced by thecontinuous estimated noise/sound reaching the user's ear which couldinduce permanent partial hearing loss. These methods and devicestypically integrate by estimation the total noise dose received by theuser's ear, considering a sound generation via the speaker inside theheadset of the user, as well as the estimated added noise contributionof the user surroundings or environmental noise as measured by andexternal microphone located on the headset. Upon the calculated totaldose reaching a pre-determined threshold, an action or protectivemeasure is taken by the processor.

These integrated total doses are estimated depending on the type ofearpiece or headset being worn by the users, and considering theirpartial occlusion of the ear canals, the estimated cumulative totaldoses are only estimations and not real measures of the ear exposures.These estimations do not take into account the actual positioning of theearpieces inside the user's ears, which may vary considerably from oneuser to another, as opposed to constant and known occlusion occurringwhen using custom-fitted in-ear devices, as disclosed in U.S. Pat. No.6,754,357 granted to McIntosh et al., U.S. Pat. No. 6,687,377 granted toVoix et al., and U.S. Pat. No. 7,688,983 granted to Voix et al.Furthermore, these estimated integrations do not take into considerationthe fact that the human ear rests, or recuperates from auditory fatigueover time, especially when the sound pressure level or the ambient noiseis relatively low.

With the always increasing popularity of personal music players (PMP) orthe like, users tend to constantly wear the headphones to listen musicor the like. In such cases, the users essentially become acousticallydisconnected, at least partially, from surrounding ambient sounds and/ornoises, which could cause dangerous situations. In order to be inhearing contact with the environment, the users need to eithersignificantly reduce the sound or playback volume of the PMP or removeat least one of the two headphones, which might become annoying,especially if that kind of situation occurs frequently.

Many documents such as U.S. Pat. No. 3,819,860 granted to Miller, U.S.Pat. No. 6,754,359 granted to Svean et al., and U.S. Pat. No. 7,502,484granted to Ngia et al. teach an ear terminal with an internal microphonefor clean voice pickup from the user. This measured voice signal,although clean (essentially noiseless), is not a natural speech voicesince the higher frequencies have essentially been transformed, by thesurrounding body parts, into lower frequencies, giving the impression ofan occlusion effect in that the voice is muffled or captured from insidea box, or closed cavity or the like, such that it is not preferred fortransmission via a telecommunication network or the like.

Accordingly, there is a need for an improved earpiece device and method.

SUMMARY OF THE INVENTION

It is therefore a general object of the present invention to provide animproved earpiece device and method that obviate the above-mentioneddisadvantages.

An advantage of the present invention is that the earpiece deviceprovides for a more accurate calculation of the total noise dosereaching a specific ear, by taking advantage of using a custom-fittedin-ear device (with improved occlusion of the ear canal), which allowsevaluation of occurring sound bursts, and measuring the actual impactthereof inside the occluded ear canal, behind the earpiece.

Another advantage of the present invention is that the earpiece deviceconsiders a relative ear fatigue recuperation over time whencontinuously calculating the cumulated total noise or sound dose.

A further advantage of the present invention is that the earpiece devicecan detect if the earpiece is actually being worn by the user or not,and reflect this situation into the calculation of the cumulated totalnoise or sound dose.

Yet another advantage of the present invention is that the earpiecedevice provides for a more accurate calculation of the total sound dosereaching a specific ear.

Another advantage of the present invention is that the earpiece deviceprovides for the user to selectively disable the audio signal reachingthe speaker of the headphone(s) temporarily, permanently or for apredetermined time duration, and allow the user to hear, via theheadphone speaker, the external ambient noise measured by an externalmicrophone located on the corresponding headphone.

A further advantage of the present invention is that the earpiece deviceprovides to the user the capability of individually varying the ratio ofsound volume playing in the background (external microphone) and of theaudio source to mix or crossfade the signals before they are beingplayed by the speaker of the earpiece.

Yet a further advantage of the present invention is that the earpiecedevice provides for ambient sound noise gating (ASNG) to allow theexternal ambient noise measured by the corresponding external microphoneto be gated in removing the excessive ambient noise therefrom and keeponly noise emerging signals.

Yet another advantage of the present invention is that the earpiecedevice allows the user to select a desired gate threshold for the ASNG,thereby adjusting the sensitivity level of the ambient noise to betransferred to the speaker of the corresponding headphone speaker.

Still another advantage of the present invention is that the earpiecedevice, in transmitting the ambient noise measured by the correspondingexternal microphone, ensures an unaltered localization of the incomingnoise that enables the user to detect the source direction of thatambient noise because of the localization of the external microphone inclose proximity of the corresponding user's ear.

Another advantage of the present invention is that the earpiece deviceprovides for user's voice pickup from the user's ear for transmissionthereof, via an earpiece internal microphone.

Still another advantage of the present invention is that the earpiecedevice provides for simultaneous user's voice pickup from an earpieceexternal microphone, which allows for a combination of the two internaland external microphone signals for clearer and more acousticallynatural voice, which combination depends on the comparison between thetwo signals to prevent ambient noise perturbations, whenever applicable.

According to an aspect of the present invention, there is provided asound dose limiter device for controlling a total sound dose reaching anear of a user, said limiter device comprising:

-   an in-ear device for substantially occluding an outer ear canal of    the user, said in-ear device including a speaker for providing an    audio signal input from an audio output of an audio source inside    the outer ear canal, an internal microphone for measuring a sound    pressure level inside the occluded outer ear canal, and an external    microphone for measuring an external ambient sound pressure level    reaching the user's ear; and-   a controller device connecting to the internal and external    microphones for receiving respective internal and external measured    sound pressure levels and for receiving the audio output, said    controller device performing an evaluation of the internal and    external measured sound pressure levels, calculating a cumulative    total sound dose from the internal sound pressure level and the    audio signal input depending on the evaluation, and controlling the    audio signal input transmitted to the speaker.

In one embodiment, the controller device further calculates, based on alevel of the audio signal input, an estimated sound dose decrease so asto account for a fatigue recuperation of the user's ear over time, theestimated sound dose decrease being subtracted from the cumulative totalsound dose.

Conveniently, the controller device repeatedly performs the evaluationand calculations over a predetermined time interval.

In one embodiment, the controller device further includes a displayconnecting to the controller device, said display displaying aninformation from the controller device corresponding to the calculatedcumulative total sound dose.

Conveniently, the controller device further calculates an estimatedlistening remaining time of transmission of the audio output to theaudio signal input before the calculated cumulative total sound dosereaches a maximum acceptable sound dose threshold based on the internalsound pressure level and/or the audio signal input depending on theevaluation.

Typically, the information is the estimated remaining listening time.

Conveniently, upon the estimated calculated cumulative total sound doseapproaching the maximum acceptable sound dose threshold within apredetermined time threshold, the controller device further transmits awarning signal to the display and/or the speaker.

Alternatively, upon the estimated calculated cumulative total sound doseapproaching or reaching the maximum acceptable sound dose thresholdwithin a predetermined time threshold, the controller device furthertakes an auditory action.

Conveniently, the auditory action is a progressive decrease of the audiosignal input transmitted to the speaker.

Alternatively, the auditory action is a stop of transmission of theaudio signal input to the speaker.

According to another aspect of the present invention, there is provideda method for calculating a total sound dose reaching an ear of a userwearing an in-ear device substantially occluding a user's outer earcanal, the in-ear device including a speaker for providing an audiosignal input from an audio output of an audio source inside the outerear canal, an internal microphone for measuring a sound pressure levelinside the occluded outer ear canal, and an external microphone formeasuring an external ambient sound pressure level reaching the user'sear, said method comprising the steps of:

-   measuring, during a predetermined time interval, the internal and    external sound pressure levels, and the audio output;-   performing an evaluation of the internal and external measured sound    pressure levels;-   calculating a current interval total sound dose from the internal    sound pressure level and the audio signal input depending on the    evaluation, and a cumulative total sound dose based on previous time    intervals; and-   controlling the audio signal input transmitted to the speaker.

In one embodiment, the step of calculating includes calculating, basedon a level of the audio signal input, a current interval estimated sounddose decrease so as to account for a fatigue recuperation of the user'sear over time, the estimated sound dose decrease being subtracted fromthe cumulative total sound dose.

Conveniently, the step of evaluating includes comparing, over thepredetermined time interval, the internal and external sound pressurelevels to determine if both correlate and/or are coherent with oneanother, and if the external sound pressure level is larger than theinternal sound pressure level by at least a predetermined leveldifference; and

wherein the step of calculating includes calculating a current intervaltotal sound dose from the audio signal input when the internal andexternal sound pressure levels do not correlate and/or are not coherentwith one another, form the internal sound pressure level when theinternal and external sound pressure levels correlate and/or arecoherent with one another and when the external sound pressure level isnot larger than the internal sound pressure level by at least thepredetermined level difference, and from an addition of the audio signalinput and the internal sound pressure level when the internal andexternal sound pressure levels correlate and/or are coherent with oneanother and when the external sound pressure level is larger than theinternal sound pressure level by at least the predetermined leveldifference.

In one embodiment, the step of controlling includes displaying aninformation corresponding to the calculated cumulative total sound doseonto a display.

Conveniently, the step of calculating includes estimating a listeningremaining time of transmission of the audio output to the audio signalinput before the calculated cumulative total sound dose reaches amaximum acceptable sound dose threshold based on the internal soundpressure level and/or the audio signal input depending on theevaluation.

Typically, the step of controlling includes displaying the estimatedlistening remaining time.

In one embodiment, the step of calculating includes determining if thecalculated cumulative total sound dose approaches a maximum acceptablesound dose threshold, and

wherein the step of controlling includes, upon the calculated cumulativetotal sound dose approaching the maximum acceptable sound dosethreshold, transmitting a warning signal to the display and/or thespeaker.

In one embodiment, the step of controlling includes, upon the calculatedcumulative total sound dose approaching or reaching the maximumacceptable sound dose threshold, taking an auditory action.

In one embodiment, the step of controlling includes, upon the calculatedcumulative total sound dose approaching or reaching the maximumacceptable sound dose threshold within a predetermined time threshold,progressively decreasing the audio signal input transmitted to thespeaker.

Conveniently, the step of controlling includes, upon the calculatedcumulative total sound dose approaching or reaching the maximumacceptable sound dose threshold within a predetermined time threshold,progressively stopping transmission of the audio signal input to thespeaker.

In one embodiment, the user wears two similar said in-ear devicesubstantially occluding a corresponding said user's outer ear canal, thestep of calculating includes calculating, for each said user's ear, acorresponding current interval total sound dose from the internal soundpressure level and the audio signal input depending on the evaluation,and a cumulative total sound dose based on previous time intervals andthe largest one of the two said current interval total sound doses.

According to another aspect of the present invention, there is provideda push-to-hear device for allowing an external ambient sound to be heardby an ear of a user, said push-to-hear device comprising:

-   at least one in-ear device for substantially occluding an outer ear    canal of the user, said at least one in-ear device including a    speaker for providing an audio signal input from an audio output of    an audio source inside the outer ear canal, and an external    microphone for measuring an external ambient sound pressure level    reaching the user's ear; and-   a controller device connecting to the external microphone for    receiving an external measured sound pressure level and for    receiving the audio output, said controller device including an    activation switch device activatable by the user, said controller    device allowing the audio output to reach the speaker when the    activation switch device is unactivated, and allowing the external    ambient sound pressure level to reach the speaker when the    activation switch device is activated, while at least partially    disabling the audio output from reaching the speaker.

In one embodiment, the controller device allows the external ambientsound pressure level to reach the speaker when the activation switchdevice is activated, while totally disabling the audio output fromreaching the speaker.

In one embodiment, the controller device further automatically anddigitally adjusts the external ambient sound pressure level for anatural sounding thereof at the speaker of the in-ear device.

In one embodiment, the controller device further includes a secondactivation command device activatable by the user, said secondactivation command device allowing a predetermined value of a soundvolume ratio of the external ambient sound pressure level over the audiooutput to reach the speaker when the second activation command device isactivated, said second activation command device, when activated,deactivating said activation switch device.

Conveniently, the second activation command device further allows theuser to modify the predetermined value of the sound volume ratio so asto vary the blending ratio thereof reaching the speaker when the secondactivation command device is activated.

In one embodiment, the controller device further includes an ambientsound noise gating filter device activatable by the user, said ambientsound noise gating filter device, when activated, eliminating a noiseportion of the external ambient sound pressure level having an acousticpressure smaller than a predetermined gating threshold from the externalambient sound pressure level so as to keep only a noise-emerging portionthereof at the speaker of the in-ear device.

Conveniently, the predetermined gating threshold is adjustable by theuser.

According to another aspect of the present invention, there is provideda method for allowing an external ambient sound to be heard by an ear ofa user wearing an in-ear device substantially occluding a user's outerear canal, the in-ear device including a speaker for providing an audiosignal input from an audio output of an audio source inside the outerear canal, and an external microphone for measuring an external ambientsound pressure level reaching the user's ear, said method comprising thesteps of:

-   upon activation of an activation switch device activatable by the    user, measuring the external ambient sound pressure level; and-   allowing the external ambient sound pressure level to reach the    speaker, while at least partially disabling the audio output from    reaching the speaker.

In one embodiment, the step of allowing includes allowing the externalambient sound pressure level to reach the speaker, while totallydisabling the audio output from reaching the speaker.

In one embodiment, the step of allowing includes automatically anddigitally adjusting the external ambient sound pressure level for anatural sounding thereof at the speaker of the in-ear device.

In one embodiment, the method further includes the steps of:

-   upon activation of second activation command device activatable by    the user, automatically deactivating said activation switch device    and measuring the external ambient sound pressure level; and-   allowing a predetermined value of a sound volume ratio of the    external ambient sound pressure level over the audio output to reach    the speaker.

Conveniently, the method further includes the step of:

-   allowing the user to modify the predetermined value of the sound    volume ratio so as to vary the blending ratio thereof reaching the    speaker when the second activation command device is activated.

In one embodiment, the method further includes the step of:

-   upon activation of an ambient sound noise gating filter device    activatable by the user, eliminating a noise portion of the external    ambient sound pressure level having an acoustic pressure smaller    than a predetermined gating threshold from the external ambient    sound pressure level, whereby keeping only a noise-emerging portion    thereof at the speaker of the in-ear device.

Conveniently, the method further includes the step of:

-   allowing the user to modify said predetermined gating threshold.

According to another aspect of the present invention, there is provideda communication device for allowing a voice of a user to be transmittedto a telecommunication transmission link, said communication devicecomprising:

-   an in-ear device for substantially occluding an outer ear canal of    the user, said in-ear device including an internal microphone for    measuring a sound pressure level inside the occluded outer ear    canal, and an external microphone for measuring an external ambient    sound pressure level reaching the user's ear, the internal and    external measured sound pressure levels including respective    acoustically deformed speech voice from the user; and-   a controller device connecting to the internal and external    microphones for receiving respective internal and external measured    sound pressure levels, said controller device performing an    evaluation of the external measured sound pressure level, digitally    generating an enhanced natural speech voice signal from at least the    internal sound pressure level depending on the evaluation, and    transmitting the generated enhanced natural speech voice signal to    the telecommunication transmission link.

In one embodiment, the controller device further generates the enhancednatural speech voice signal from the internal sound pressure level whenthe external measured sound pressure level is larger than a noisethreshold.

Conveniently, when the external measured sound pressure level is smalleror equal to the noise threshold, the controller device generates theenhanced natural speech voice signal from both the internal and externalsound pressure levels with greater content of the external soundpressure level than of the internal sound pressure level when theinternal sound pressure level is generally larger than the externalsound pressure level, and with greater content of the internal soundpressure level than of the external sound pressure level when theinternal sound pressure level is generally smaller than the externalsound pressure level.

Typically, when generating the enhanced natural speech voice signal fromboth the internal and external sound pressure levels, the controllerdevice substantially combines, over a human voice frequency band, a highfrequency portion of the external sound pressure level with a lowfrequency portion of the internal sound pressure level to generate theenhanced natural speech voice signal.

Alternatively, when the external measured sound pressure level issmaller or equal to the noise threshold, the controller device generatesthe enhanced natural speech voice signal from both the internal andexternal sound pressure levels when the internal and external soundpressure levels correlate and/or are coherent with one another, and fromthe internal sound pressure level when the internal and external soundpressure levels do not correlate and/or are not coherent with oneanother.

Typically, when generating the enhanced natural speech voice signal fromboth the internal and external sound pressure levels, said controllerdevice substantially combines, over a human voice frequency band, a highfrequency portion of the external sound pressure level with a lowfrequency portion of the internal sound pressure level to generate theenhanced natural speech voice signal.

According to another aspect of the present invention, there is provideda method for transmitting a voice of a user wearing an in-ear devicesubstantially occluding a user's outer ear canal to a telecommunicationtransmission link, the in-ear device including an internal microphonefor measuring a sound pressure level inside the occluded outer earcanal, and an external microphone for measuring an external ambientsound pressure level reaching the user's ear, the internal and externalmeasured sound pressure levels including respective acousticallydeformed speech voice from the user, said method comprising the stepsof:

-   measuring the internal and external sound pressure levels;-   performing an evaluation of the external measured sound pressure    level;-   digitally generating an enhanced natural speech voice signal from at    least the internal sound pressure level depending on the evaluation;    and-   transmitting the generated enhanced natural speech voice signal to    the telecommunication transmission link.

In one embodiment, the step of generating includes digitally generatingthe enhanced natural speech voice signal from the internal soundpressure level when the external measured sound pressure level is largerthan a noise threshold.

In one embodiment, the step of generating includes, when the externalmeasured sound pressure level is smaller or equal to the noisethreshold, digitally generating the enhanced natural speech voice signalfrom both the internal and external sound pressure levels with greatercontent of the external sound pressure level than of the internal soundpressure level when the internal sound pressure level is generallylarger than the external sound pressure level, and with greater contentof the internal sound pressure level than of the external sound pressurelevel when the internal sound pressure level is generally smaller thanthe external sound pressure level.

Conveniently, the step of generating includes, when generating theenhanced natural speech voice signal from both the internal and externalsound pressure levels, substantially combining, over a human voicefrequency band, a high frequency portion of the external sound pressurelevel with a low frequency portion of the internal sound pressure levelto generate the enhanced natural speech voice signal.

In one embodiment, the step of generating includes, when the externalmeasured sound pressure level is smaller or equal to the noisethreshold, digitally generating the enhanced natural speech voice signalfrom both the internal and external sound pressure levels when theinternal and external sound pressure levels correlate and/or arecoherent with one another, and from the internal sound pressure levelwhen the internal and external sound pressure levels do not correlateand/or are not coherent with one another.

Conveniently, the step of generating includes, when generating theenhanced natural speech voice signal from both the internal and externalsound pressure levels, substantially combining, over a human voicefrequency band, a high frequency portion of the external sound pressurelevel with a low frequency portion of the internal sound pressure levelto generate the enhanced natural speech voice signal.

Other objects and advantages of the present invention will becomeapparent from a careful reading of the detailed description providedherein, with appropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects and advantages of the present invention will becomebetter understood with reference to the description in association withthe following Figures, in which similar references used in differentFigures denote similar components, wherein:

FIG. 1 is a simplified schematic bloc diagram of an advancedcommunication earpiece device in accordance with an embodiment of thepresent invention, referring to a noise and music dose limiter (MDL)device, and a push-to-hear (PTH) device, and an in-ear microphone (IEM)device;

FIG. 2 is a simplified flow chart of an advanced communication earpiecemethod in accordance with an embodiment of the present invention,referring to a method of operation of the noise and music dose limiter(MDL) device of FIG. 1;

FIG. 3 is a simplified flow chart of an advanced communication earpiecemethod in accordance with an embodiment of the present invention,referring to a method of operation of the push-to-hear (PTH) device ofFIG. 1;

FIG. 4A is a simplified flow chart of an advanced communication earpiecemethod in accordance with an embodiment of the present invention,referring to a method of operation of the in-ear microphone (IEM) deviceof FIG. 1; and

FIG. 4B is similar to FIG. 4A, showing an alternate method of operationof the in-ear microphone (IEM) device of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the annexed drawings the preferred embodiments of thepresent invention will be herein described for indicative purpose and byno means as of limitation.

Referring now in more detail to FIGS. 1 and 2, there is shown simplifiedschematic bloc diagram of an embodiment 10 of an advanced communicationearpiece device, as a sound or music dose limiter device, and a methodfor using the device in accordance with the present invention. The noiseand music dose limiter (MDL) 10 typically includes a controller unit 12connected to at least one, preferably a pair of custom-fitted in-eardevices 14 (only one being shown), such that the respective outer earcanal 15 of the user is essentially occluded thereby (snugly fit), forconnection to an audio output of an audio source 16 such as a personalmusic player (PMP) or the like, or any electronic device adapted to sendan audio signal to the speaker 18 of the each in-ear device 14,typically left and right devices.

In addition to the speaker 18, each in-ear device 14 includes aninternal microphone 20 (Min) for measuring the sound/noise level insidethe ear occluded canal 15, between the in-ear device 14 and the tympanicmembrane, and an external microphone 22 (Mout) for measuring theexternal ambient sound/noise level reaching the corresponding outer earof the user. These internal and external measured sound pressure levels,from internal 20 and external 22 microphones, of each in-ear device 14,as well as the corresponding (left or right) audio signal coming fromthe PMP 16 are input signals of the controller unit 12. Based on theseinputs, the controller unit 12 calculates the total noise dose (TND), ortotal sound dose, reaching each user's ear, and provides for a remainingtime estimate for listening to the input signal (such as music or thelike) before the TND reaches the maximum acceptable sound dose (MASD)value or threshold considered to be harmful to the user, based on themost recent measured average sound level reaching each ear as well as onthe user's own susceptibility, including physical characteristics (age,etc.), beyond which there might be some permanent hearing losses for theuser. Upon the TND approaching, reaching or exceeding the MASD value,the controlled unit 12 typically sends an audio warning signal to theuser, such as an audible repeated appropriate beep, or simply starts, atleast intermittently, reducing the volume of the sound signal, orultimately stops the audio signal sent to the speaker 18, or any otherwarning code as required.

More specifically, the controller device unit 12 performs the followingsteps in calculating the TND, for each ear, based on the internal (Min)and external (Mout) microphone measured sound pressure levels and theaudio input from the PMP 16. The calculation being done at regular timeintervals ΔT, and the different sound pressure levels measured from themicrophones 20, 22 and received from the PMP 16 are typically averagedvia an RMS (Root Mean Square) estimator. For each time interval ΔT, theevaluation consists of the measured sounds from both internal andexternal microphones 20, 22 being compared to find out if they correlate(essentially follow the same magnitude or amplitude profile over time onspecific frequency sub-bands) and/or are coherent (essentially followthe same magnitude profile over frequency in specific time frames) withone another. If not, this means that there is significantly lessexternal sound that reaches inside the occluded ear canal other than theone coming from the speaker 18, such that both measured sounds aredifferent, and the estimated acoustic pressure that reaches the tympanicarea is primarily due to the signal reaching the speaker 18, which isestimated taking into account the in-ear device loudspeaker sensitivity.If yes, the controller unit 12 then verifies if the measured sound fromthe external microphone 22 is significantly stronger, by a predeterminedlevel difference of at least a few decibels (dBs), than the one measuredby the internal microphone 20. If not, it essentially means that thein-ear device 12 is not worn by the user (since both measurements areconsidered to have similar measurands), and, in such a case, theestimated acoustic pressure that reaches the tympanic area isessentially the one reaching either microphone 20, or 22. If yes, itmeans that an external sound burst (disturbance) or the like reachedinside the occluded ear canal 15 after passing through the in-ear device14, in which case, the estimated acoustic pressure that reaches thetympanic area is due to both the sound measured by the internalmicrophone 20 that is distinct from the signal reaching the speaker 18added to the signal reaching the speaker 18.

Based on the above estimated acoustic pressure level reaching thetympanic area, for the specified time interval ΔT, a sound dose iscalculated which is then added to the cumulative noise and music dose.Furthermore, an estimated dose decrease is calculated for that same timeinterval ΔT to account for a certain ‘ear fatigue recuperation’ of theear, based on an estimated Noise Dose

Decrease Rate (NDDR), or sound dose decrease rate, which could be eitherlinear or non-linear (logarithmic or the like) over time, depending ontime as well as on the current noise level reaching the ear, andsubtracted from the cumulative sound dose (as it reduces the same) toobtain the estimated cumulative TND.

The NDDR could, for example assumes that the human ear totallyrecuperates from the MASD threshold in a few hours, such as 16 hours orthe like, in the absence of any harmful noise, such as any noise above apredetermined safe level of 70 decibels or the like. On the other hand,in the presence of harmful noise, the higher the harmful noise is, themore the hearing recuperation time increases.

As mentioned hereinabove, upon the estimated TND, the controller unit 12typically estimates, assuming a sound volume similar to the latestmeasured volume (over the last time interval, or the history of the lastfew time intervals), the remaining time (RT) for the user to listen tothe music or the like from the PMP 16, or any other similar listeningtime-related information, and transmits that information to a display 24which displays the estimated time thereon. Such a display 24 could beeither in the form of a bar meter, of multiple leds (light emittingdiodes), or a digital display. Similarly, upon the estimated TNDapproaching the MASD threshold, the controller unit 12 typically furthersends an audible warning signal to the speaker 18, such a warning signalvarying depending on the value of the estimated RT according to apredetermined warning code or the like. Ultimately, upon the estimatedTND reaching and/or exceeding the MASD threshold within a timethreshold, or one of a plurality of time thresholds, the controller unit12 typically further simply starts, at least intermittently, reducingthe volume of the sound signal, or ultimately stops the audio signalsent to the speaker 18, and also typically displays the correspondingsituation of the display 24.

When both in-ear devices 14 are used, the controller unit 12 typicallycalculates only one TND, taking into consideration the worst (highest)estimated TND of the two devices 14 for each time interval ΔT.

Now referring more specifically to FIGS. 1 and 3, there is shownsimplified schematic bloc diagram of an embodiment 110 of an advancedcommunication earpiece device, as a push-to-hear device, and a methodfor using the device in accordance with the present invention. Thepush-to-hear (PTH) device 110 typically includes a controller unit 112connected to at least one, preferably a pair of custom-fitted in-eardevices 14 (only one being shown), such that the respective ear canal 15of the user is essentially occluded thereby, for connection to an audiooutput of a personal music player (PMP) 16 or the like, or anyelectronic device adapted to send an audio signal to the speaker 18 ofthe each in-ear device 14, typically left and right devices.

In addition to the speaker 18, each in-ear device 14 of the PTH device110 includes at least an external microphone 22 (Mout) for measuring theexternal ambient sound/noise reaching the corresponding ear or the user.The controller unit 112 typically includes an on/off activation switchto activate/deactivate the controller 112. When activated, thecontroller 112 disconnects the audio input from the PMP 16 from theheadphone speakers 18 and connects the ambient sound measured by thecorresponding external microphone 22 to the speakers 18, as representedby toggle switch 126, to enable the user to selectively and temporarilyhear the ambient sound rather than the music or the like. Although notillustrated, when activated, the controller unit 112 could alternativelyautomatically switch back the device 110 to reconnect the audio signalfrom the PMP 16 instead of the ambient sound from the externalmicrophone 22 after a predetermined lapse of time has occurred, such as30 seconds, one minute or the like.

Alternatively, the PTH device 110 has a second activation/deactivationcommand, such as by simultaneously pressing two buttons or the like, asthe two up (‘+’) and down (‘−’) volume buttons 128, during apredetermined time duration (such as 2 second or the like) for thecontroller unit 112 to allow both the audio signal from the PMP 16 andthe ambient sound from the external microphone 22 to be simultaneouslyconnected to the headphone speaker 18, and also press either the upand/or down volume buttons 128 to increase or decrease the sound volumeratio (SVR), or blending ratio, of the ambient sound over the audiosignal.

The PTH device 110 typically provides for automatic, preferably digital,adjustment of the ambient noise measured from the external microphone 22and transmitted to the headphone speaker 18 for a natural soundingthereof, the gain and frequency response adjustments depending on theactual type of headphone speaker and in-ear device.

Additionally, the PTH device 110 typically includes a user activatableelectronic filter 130 of the ambient sound/noise signal measured by theexternal microphone 22. The ambient sound noise gating (ASNG) filter 130essentially eliminates the noise portion of the ambient signal to keeponly the noise emerging-type signals having an acoustic pressure largerthan or above a gating threshold (GT). Preferably, the gating thresholdGT, or microphone sensitivity threshold, is also adjustable by the uservia up (‘+’) and down (‘−’) volume buttons 132 or the like.Alternatively, as an example, instead of using specific buttons 132, thesame two buttons 128 could also be used for the GT adjustment, as longas the two buttons are simultaneously pressed during a secondpredetermined time duration, typically longer than the first one, foractivation/deactivation of the ASNG filter 130.

Typically, the ASNG filter 130 can be used at any time during theoperation of the PTH device 110, whichever option is selected by theuser.

Now referring more specifically to FIGS. 1, 4A and 4B, there is shownsimplified schematic bloc diagram of an embodiment 210 of an advancedcommunication earpiece device, as an inside-the-ear microphone device,and a method for using the device in accordance with the presentinvention. The in-ear microphone (IEM) device 210 typically includes acontroller unit 212 connected to at least one custom-fitted in-eardevice 14, such that the corresponding outer ear canal 15 of the user isessentially occluded thereby (snugly fit).

In addition, the in-ear device 14 includes an internal microphone 20(Min) for measuring the sound/noise, and also the user's voice insidethe ear canal 15, between the in-ear device 14 and the tympanicmembrane, and an external microphone 22 (Mout) for measuring theexternal ambient sound/noise reaching the corresponding ear or the user.These internal and external measured noises, from internal 20 andexternal 22 microphones, of the in-ear device 14 are input signals ofthe controller unit 212.

Based on these inputs, the controller unit 212 evaluates if the RMSvalue of the external noise is smaller or equal to a first noisethreshold (NT). If not, this means that the external ambient noise istoo loud and disturbs any sound voice that would be simultaneouslymeasured by the external microphone 22. The user's voice is thereforecaptured by the internal microphone 20 before it is sent by thecontroller unit 212 of the IEM device 210 to a telecommunicationtransmission link (TTL), such as a Bluetooth™ system wireless link, atelephone or the like. In such a case, since the speech voice measuredfrom the ear canal of the user is acoustically deformed, the controllerunit 212 typically and digitally transforms the deformed speech voiceinto an enhanced speech signal (recreating especially the higherfrequencies) which sounds more like a natural speech voice (NSV) fromone's mouth.

The user's voice can be captured using either only the externalmicrophone 22, by internal microphone 20 or by a combination (blending)of both signals from external microphone 22 and internal microphone 20.The controller unit 212 continuously monitors the levels and frequencycharacteristics of both external and internal picked-up signals anddecides on the ratio to be applied to the blending of both signals. In aquiet environment, the user's voice will be primarily picked-up by theexternal microphone 22 that offers natural sound quality because of theextended frequency response. In a louder environment a mix of bothmicrophone signals will be applied, using the internal microphone 20 asthe primary reference signal and merging it with the high-frequencycomponents of the voice signal picked-up by external microphone 22.Finally in a very loud environment, where the external microphone signalis unusable, only the internal microphone signal is used, and possiblyenhanced with the aforementioned digital high-frequency reclamationprocessing. Since the ambient noise level in a given environment will bechanging over time, the mixing algorithm of the controller unit 212 willconstantly adapt the mixing ratio accordingly, with appropriate signalsmoothing and cross-fading.

In the case the RMS value of the external noise is smaller or equal toNT, the measured sounds from both internal and external microphones 20,22 are compared to find out if they correlate (essentially follow thesame magnitude or amplitude profile over time on specific frequencysub-bands) and/or are coherent (essentially follow the same magnitudeprofile over frequency in specific time frames) with one another, bybeing above a second correlation threshold CT. If not, this means thatthe external noise, although not too loud, is significant enough insidethe speech frequency band to alter the user's voice measured by theexternal microphone 22, and as above, only the signal captured by theinternal microphone 20 is considered and preferably transformed by thecontroller unit 212 of the IEM device 210 into a NSV to be sent to theTTL. If yes, the controller unit 12 generates a combination of both theinternal signal for preferably lower frequencies (LF) and externalsignal for preferably higher frequencies (HF), over the typical humanvoice frequency band to generate the best user's speech voice as the NSVsignal to be sent to the TTL, as shown in FIG. 4A.

As shown in the embodiment 210′ of FIG. 4B, an alternative approach,when the RMS value of the external noise is smaller or equal to NT, isto compare the levels of both the external 22 and internal 20microphones and to assess if the wearer is speaking in a quiet butreverberant environment. In such case the external microphone 22 mightpick-up a high signal level solely caused by the wearer's voicereflections. With the internal signal being generally larger than theexternal signal, a mix of both signals are considered by the controllerunit 212 with greater content of external signal than internal signal,while with the external signal being larger than the internal signal,greater content of the internal signal is considered than the externalsignal. It is noted that the ratio of both signals for that latestcomparison is typically different than 1:1 and typically depends ondigital processing of the signals which incorporates an experimentallyderived scaling factor. In order to avoid the controller unit 212tendency to discard the signal from the external microphone 22 becauseof its high level, the internal microphone signal is then tested foruser's voice content. If user is assessed to be speaking, both theexternal and internal signals are merged before being sent to the TTL.On the other hand, if no voice signal is present on the internalmicrophone, the external microphone signal will be faded-out from themix by the controller unit 212.

Although the present advanced communication earpiece device embodimentsand methods of use have been described with a certain degree ofparticularity, it is to be understood that the disclosure has been madeby way of example only and that the present invention is not limited tothe features of the embodiments described and illustrated herein, butincludes all variations and modifications within the scope of theinvention as hereinafter claimed.

1. A sound dose limiter device for controlling a total sound dosereaching an ear of a user, said limiter device comprising: an in-eardevice for substantially occluding an outer ear canal of the user, saidin-ear device including a speaker for providing an audio signal inputfrom an audio output of an audio source inside the outer ear canal, aninternal microphone for measuring a sound pressure level inside theoccluded outer ear canal, and an external microphone for measuring anexternal ambient sound pressure level reaching the user's ear; and acontroller device connecting to the internal and external microphonesfor receiving respective internal and external measured sound pressurelevels and for receiving the audio output, said controller deviceperforming an evaluation of the internal and external measured soundpressure levels, calculating a cumulative total sound dose from theinternal sound pressure level and the audio signal input depending onthe evaluation, and decreasing the audio signal input transmitted to thespeaker based on the calculated cumulative total sound dose approachinga maximum acceptable sound dose threshold.
 2. The sound dose limiterdevice of claim 1, wherein said controller device further calculates,based on a level of the audio signal input, an estimated sound dosedecrease so as to account for a fatigue recuperation of the user's earover time, the estimated sound dose decrease being subtracted from thecumulative total sound dose.
 3. The sound dose limiter device of claim2, wherein said controller device repeatedly performs the evaluation andcalculations over a predetermined time interval.
 4. The sound doselimiter device of claim 2, further including a display connecting to thecontroller device, said display displaying an information from thecontroller device corresponding to the calculated cumulative total sounddose.
 5. The sound dose limiter device of claim 4, wherein saidcontroller device further calculates an estimated listening remainingtime of transmission of the audio output to the audio signal inputbefore the calculated cumulative total sound dose reaches the maximumacceptable sound dose threshold based on the internal sound pressurelevel and/or the audio signal input depending on the evaluation.
 6. Thesound dose limiter device of claim 5, wherein said information is theestimated remaining listening time.
 7. The sound dose limiter device ofclaim 5, wherein, upon the estimated calculated cumulative total sounddose approaching the maximum acceptable sound dose threshold within apredetermined time threshold, said controller device further transmits awarning signal to the display and/or the speaker.
 8. The sound doselimiter device of claim 5, wherein, upon the estimated calculatedcumulative total sound dose approaching or reaching the maximumacceptable sound dose threshold within a predetermined time threshold,said controller device further takes an auditory action.
 9. The sounddose limiter device of claim 8, wherein the auditory action is aprogressive decrease of the audio signal input transmitted to thespeaker.
 10. The sound dose limiter device of claim 8, wherein theauditory action is a stop of transmission of the audio signal input tothe speaker.
 11. A method for calculating a total sound dose reaching anear of a user wearing an in-ear device substantially occluding a user'souter ear canal, the in-ear device including a speaker for providing anaudio signal input from an audio output of an audio source inside theouter ear canal, an internal microphone for measuring a sound pressurelevel inside the occluded outer ear canal, and an external microphonefor measuring an external ambient sound pressure level reaching theuser's ear, said method comprising the steps of: measuring, during apredetermined time interval, the internal and external sound pressurelevels, and the audio output; performing an evaluation of the internaland external measured sound pressure levels; calculating a currentinterval total sound dose from the internal sound pressure level and theaudio signal input depending on the evaluation, and a cumulative totalsound dose based on previous time intervals; and decreasing the audiosignal input transmitted to the speaker based on the calculatedcumulative total sound dose approaching a maximum acceptable sound dosethreshold.
 12. The method of claim 11, wherein the step of calculatingincludes calculating, based on a level of the audio signal input, acurrent interval estimated sound dose decrease so as to account for afatigue recuperation of the user's ear over time, the estimated sounddose decrease being subtracted from the cumulative total sound dose. 13.The method of claim 12, wherein the step of evaluating includescomparing, over the predetermined time interval, the internal andexternal sound pressure levels to determine if both correlate and/or arecoherent with one another, and if the external sound pressure level islarger than the internal sound pressure level by at least apredetermined level difference; and wherein the step of calculatingincludes calculating a current interval total sound dose from the audiosignal input when the internal and external sound pressure levels do notcorrelate and/or are not coherent with one another, form the internalsound pressure level when the internal and external sound pressurelevels correlate and/or are coherent with one another and when theexternal sound pressure level is not larger than the internal soundpressure level by at least the predetermined level difference, and froman addition of the audio signal input and the internal sound pressurelevel when the internal and external sound pressure levels correlateand/or are coherent with one another and when the external soundpressure level is larger than the internal sound pressure level by atleast the predetermined level difference.
 14. The method of claim 12,wherein the step of controlling includes displaying an informationcorresponding to the calculated cumulative total sound dose onto adisplay.
 15. The method of claim 14, wherein the step of calculatingincludes estimating a listening remaining time of transmission of theaudio output to the audio signal input before the calculated cumulativetotal sound dose reaches the maximum acceptable sound dose thresholdbased on the internal sound pressure level and/or the audio signal inputdepending on the evaluation.
 16. The method of claim 15, wherein thestep of controlling includes displaying the estimated listeningremaining time.
 17. The method of claim 15, wherein the step ofcalculating includes determining if the calculated cumulative totalsound dose approaches a maximum acceptable sound dose threshold, andwherein the step of controlling includes, upon the calculated cumulativetotal sound dose approaching the maximum acceptable sound dosethreshold, transmitting a warning signal to the display and/or thespeaker.
 18. The method of claim 15, wherein the step of controllingincludes, upon the calculated cumulative total sound dose approaching orreaching the maximum acceptable sound dose threshold, taking an auditoryaction.
 19. The method of claim 15, wherein the step of controllingincludes, upon the calculated cumulative total sound dose approaching orreaching the maximum acceptable sound dose threshold within apredetermined time threshold, progressively decreasing the audio signalinput transmitted to the speaker.
 20. The method of claim 15, whereinthe step of controlling includes, upon the calculated cumulative totalsound dose approaching or reaching the maximum acceptable sound dosethreshold within a predetermined time threshold, progressively stoppingtransmission of the audio signal input to the speaker.
 21. The method ofclaim 11, wherein the user wears two similar said in-ear devicesubstantially occluding a corresponding said user's outer ear canal, thestep of calculating includes calculating, for each said user's ear, acorresponding current interval total sound dose from the internal soundpressure level and the audio signal input depending on the evaluation,and a cumulative total sound dose based on previous time intervals andthe largest one of the two said current interval total sound doses. 22.A push-to-hear device for allowing an external ambient sound to be heardby an ear of a user, said push-to-hear device comprising: at least onein-ear device for substantially occluding an outer ear canal of theuser, said at least one in-ear device including a speaker for providingan audio signal input from an audio output of an audio source inside theouter ear canal, and an external microphone for measuring an externalambient sound pressure level reaching the user's ear; and a controllerdevice connecting to the external microphone for receiving an externalmeasured sound pressure level and for receiving the audio output, saidcontroller device including an activation switch device activatable bythe user, said controller device allowing the audio output to reach thespeaker when the activation switch device is unactivated, and allowingthe external ambient sound pressure level to reach the speaker when theactivation switch device is activated, while at least partiallydisabling the audio output from reaching the speaker, said controllerdevice further including an ambient sound noise gating filter deviceactivatable by the user, said ambient sound noise gating filter device,when activated, eliminating a noise portion of the external ambientsound pressure level having an acoustic pressure smaller than apredetermined gating threshold from the external ambient sound pressurelevel so as to keep only a noise-emerging portion thereof at the speakerof the in-ear device.
 23. The push-to-hear device of claim 22, whereinsaid controller device allows the external ambient sound pressure levelto reach the speaker when the activation switch device is activated,while totally disabling the audio output from reaching the speaker. 24.The push-to-hear device of claim 22, wherein said controller devicefurther automatically and digitally adjusts the external ambient soundpressure level for a natural sounding thereof at the speaker of thein-ear device.
 25. The push-to-hear device of claim 22, wherein saidcontroller device further includes a second activation command deviceactivatable by the user, said second activation command device allowinga predetermined value of a sound volume ratio of the external ambientsound pressure level over the audio output to reach the speaker when thesecond activation command device is activated, said second activationcommand device, when activated, deactivating said activation switchdevice.
 26. The push-to-hear device of claim 25, wherein said secondactivation command device further allows the user to modify thepredetermined value of the sound volume ratio so as to vary the blendingratio thereof reaching the speaker when the second activation commanddevice is activated.
 27. The push-to-hear device of claim 22, whereinsaid predetermined gating threshold is adjustable by the user.
 28. Amethod for allowing an external ambient sound to be heard by an ear of auser wearing an in-ear device substantially occluding a user's outer earcanal, the in-ear device including a speaker for providing an audiosignal input from an audio output of an audio source inside the outerear canal, and an external microphone for measuring an external ambientsound pressure level reaching the user's ear, said method comprising thesteps of: upon activation of an activation switch device activatable bythe user, measuring the external ambient sound pressure level; andallowing the external ambient sound pressure level to reach the speaker,while at least partially disabling the audio output from reaching thespeaker; upon activation of an ambient sound noise gating filter deviceactivatable by the user, eliminating a noise portion of the externalambient sound pressure level having an acoustic pressure smaller than apredetermined gating threshold from the external ambient sound pressurelevel, whereby keeping only a noise-emerging portion thereof at thespeaker of the in-ear device.
 29. The method of claim 28, wherein thestep of allowing includes allowing the external ambient sound pressurelevel to reach the speaker, while totally disabling the audio outputfrom reaching the speaker.
 30. The method of claim 28, wherein the stepof allowing includes automatically and digitally adjusting the externalambient sound pressure level for a natural sounding thereof at thespeaker of the in-ear device.
 31. The method of claim 28, furtherincluding the steps of: upon activation of second activation commanddevice activatable by the user, automatically deactivating saidactivation switch device and measuring the external ambient soundpressure level; and allowing a predetermined value of a sound volumeratio of the external ambient sound pressure level over the audio outputto reach the speaker.
 32. The method of claim 31, further including thestep of: allowing the user to modify the predetermined value of thesound volume ratio so as to vary the blending ratio thereof reaching thespeaker when the second activation command device is activated.
 33. Themethod of claim 28, further including the step of: allowing the user tomodify said predetermined gating threshold.
 34. A communication devicefor allowing a voice of a user to be transmitted to a telecommunicationtransmission link, said communication device comprising: an in-eardevice for substantially occluding an outer ear canal of the user, saidin-ear device including an internal microphone for measuring a soundpressure level inside the occluded outer ear canal, and an externalmicrophone for measuring an external ambient sound pressure levelreaching the user's ear, the internal and external measured soundpressure levels including respective acoustically deformed speech voicefrom the user; and a controller device connecting to the internal andexternal microphones for receiving respective internal and externalmeasured sound pressure levels, said controller device performing anevaluation of the external measured sound pressure level, digitallygenerating an enhanced natural speech voice signal from the internalsound pressure level depending on the evaluation when the externalmeasured sound pressure level is larger than a noise threshold, and fromboth the internal and external sound pressure levels when the externalmeasured sound pressure level is smaller or equal to the noisethreshold, and transmitting the generated enhanced natural speech voicesignal to the telecommunication transmission link.
 35. The communicationdevice of claim 34, wherein, when the external measured sound pressurelevel is smaller or equal to the noise threshold, said controller devicegenerates the enhanced natural speech voice signal from both theinternal and external sound pressure levels with greater content of theexternal sound pressure level than of the internal sound pressure levelwhen the internal sound pressure level is generally larger than theexternal sound pressure level, and with greater content of the internalsound pressure level than of the external sound pressure level when theinternal sound pressure level is generally smaller than the externalsound pressure level.
 36. The communication device of claim 35, wherein,when generating the enhanced natural speech voice signal from both theinternal and external sound pressure levels, said controller devicesubstantially combines, over a human voice frequency band, a highfrequency portion of the external sound pressure level with a lowfrequency portion of the internal sound pressure level to generate theenhanced natural speech voice signal.
 37. The communication device ofclaim 34, wherein, when the external measured sound pressure level issmaller or equal to the noise threshold, said controller devicegenerates the enhanced natural speech voice signal from both theinternal and external sound pressure levels when the internal andexternal sound pressure levels correlate and/or are coherent with oneanother, and from the internal sound pressure level when the internaland external sound pressure levels do not correlate and/or are notcoherent with one another.
 38. The communication device of claim 37,wherein, when generating the enhanced natural speech voice signal fromboth the internal and external sound pressure levels, said controllerdevice substantially combines, over a human voice frequency band, a highfrequency portion of the external sound pressure level with a lowfrequency portion of the internal sound pressure level to generate theenhanced natural speech voice signal.
 39. A method for transmitting avoice of a user wearing an in-ear device substantially occluding auser's outer ear canal to a telecommunication transmission link, thein-ear device including an internal microphone for measuring a soundpressure level inside the occluded outer ear canal, and an externalmicrophone for measuring an external ambient sound pressure levelreaching the user's ear, the internal and external measured soundpressure levels including respective acoustically deformed speech voicefrom the user, said method comprising the steps of: measuring theinternal and external sound pressure levels; performing an evaluation ofthe external measured sound pressure level; digitally generating anenhanced natural speech voice signal from the internal sound pressurelevel depending on the evaluation when the external measured soundpressure level is larger than a noise threshold, and from both theinternal and external sound pressure levels when the external measuredsound pressure level is smaller or equal to the noise threshold; andtransmitting the generated enhanced natural speech voice signal to thetelecommunication transmission link.
 40. The method of claim 39, whereinthe step of generating includes, when the external measured soundpressure level is smaller or equal to the noise threshold, digitallygenerating the enhanced natural speech voice signal from both theinternal and external sound pressure levels with greater content of theexternal sound pressure level than of the internal sound pressure levelwhen the internal sound pressure level is generally larger than theexternal sound pressure level, and with greater content of the internalsound pressure level than of the external sound pressure level when theinternal sound pressure level is generally smaller than the externalsound pressure level.
 41. The method of claim 40, wherein the step ofgenerating includes, when generating the enhanced natural speech voicesignal from both the internal and external sound pressure levels,substantially combining, over a human voice frequency band, a highfrequency portion of the external sound pressure level with a lowfrequency portion of the internal sound pressure level to generate theenhanced natural speech voice signal.
 42. The method of claim 39,wherein the step of generating includes, when the external measuredsound pressure level is smaller or equal to the noise threshold,digitally generating the enhanced natural speech voice signal from boththe internal and external sound pressure levels when the internal andexternal sound pressure levels correlate and/or are coherent with oneanother, and from the internal sound pressure level when the internaland external sound pressure levels do not correlate and/or are notcoherent with one another.
 43. The method of claim 42, wherein the stepof generating includes, when generating the enhanced natural speechvoice signal from both the internal and external sound pressure levels,substantially combining, over a human voice frequency band, a highfrequency portion of the external sound pressure level with a lowfrequency portion of the internal sound pressure level to generate theenhanced natural speech voice signal.